Multioffice telephone system



Oct. 30, 1928. 1,689,543

. J. WICKS MULTIOFFICE TELEPHONE SYSTEM Filed March '7, 1927 7Sheets-Sheet Z -Inuen [773- Jmhn M15145 HIT y.

0a. so, 1928. 1,689543 J WICKS MULTIOFFICE TELEPHONE SYSTEM Filed March1927 '7 Sheets-$21604; 3

Irma John M'LCJkE Oct, 30,1928. 1;689,543

J. wicKs IULTIOFFICE TELEPHONE SYSTEM ,Filed March 1927 7 Sheets-Sheet'4 IIULTIOFFICE TELEPHONE SYSTEM J. WICKS 7 Sheets-Sheet 5 Filed March'7, 1927 N N N L Y N um um umm lam Oct. 30, 1928. 1,689,543

7 J. WICKS MULTIOFFICE TELEPHONE SYSTEM I Filed March '7. 1927 7Sheets-Sheet 6 ,MMHn- Oct. 30, 1928.

J. WICKS IULTIOFFICE TELEPHONE SYSTEM 7 Sheets-Sheet '7 Filed March '7,1927 -Im.ran ur- Juhn Jnfwks Patented Oct. 30, 1928.

UNITED STATES PATENTqOFFICE. J

JOHN WICKS, E OAK PARK, ILLINOIS, AssIeNo T0 REsERvE HOLDING coi/IPANY.OF KANSAS CITY, MIssoURI, A coRroR 'rIo 0E DELAWARE.

MULTIOFFICE TELEPHONE SYSTEM.

Application filed March 7, 1927. Serial No. 173,258.

The present invention relates to.'mu1tioffice telephone systems ingeneral, but is concerned more particularly with multiofiice'automatictelephone systems; and the broad general object is the production of newand improved circuit. arrangements for use in inter-oflice connectionsof' a multi office automatic telephone system wherein automatic switchesof a given type are used in one office and wherein automatic switches ofa different type fromthe "standpoint of their circuit arrangements areused in another office.

There are other objects and features of the invention whichare, for themost part, more or less incidental to the carrying out I of the mainobject above stated. These latfor objects and features will be betterunderstood after a general description has been given of the system towhiohthe inventionv has been applied.

Referring now to the accompanying drawings comprising Figs. 1-8, theyshow by means of the usual circuit diagrams a sufficient amount ofequipment in a telephone system embodying thefeatures of the inventionto enable the invention to be understood. Fig. 1 is atrunking diagramshowing switch trains in two offices of a system, the switches used inthe respective switch trains being of different types from acircuitstandpoint. Figs. 2-6 are circuit diagrams showing in detail certaincircuits to be hereinafter explained; Fig. 7 is a'sheet layoutshowing'how the sheets on which Figs. 26 are drawn should be placed together in.order to be understood best; and Fig. 8 is a circuit diagram showing analternative method of effecting a certain connection to be hereinafterexplained.

Referring now particularly to Fig. 1, the equipment indicated in thisdrawing is assumed to be located in two offices X and Y of amulti-ofiice automatic telephone system,

- the dotted line down the center of the sheet indicating the dividingline between the two offices. The switches in office X are operatedaccording to the two-wire method of control over thetwo sides of thecalling line in series, talking current in local connections beingsupplied to both parties from the con nector (last switch in the train).In office Y, the'usual two-wire loop control is excrcised over thecalling line. The talking current for the called line is supplied fromthe final switch of the train, but the talkingcur rent for thecallingline is supplied from the first switch in the train, this first switchbeing a so-called first selector repeater. Accordingly, in office Y, allswitches, after the first, operate responsive to impulses repeated fromthe first selector repeater and not over the calling line loop as inoffice X. i

Referring now to office X, two subscribers lines are shown entering thisoflice. One line is the line of substation Al, and the other line is theline of substation A2. It

is assumed that office X is office No. in I t substation A1 and itcompletes aconnection whenthe associated line is calling to a firstselector such as the selector S1. The selector S1 is the office selectorand trunk lines Lextend from the various levels thereofto the variousoffices of the system. Forexample the. trunk lines extend from the fifthlevel to. local thousands selectors, one of -w,hich is the thousandsselector S2. The

coming from the sixth level of the. selector S1 in office Xand theincoming thousands selector SR3 in office Y. This repeater is usedprimarily to permit the use of a twoconductor inter-office trunk insteadof a three-conductor trunk which would be required if the repeaterwere-not used. vAt thispoint, it may be mentioned that the circuitdetails of the switches shown in ofiice X are not shown in the presentapplication and that these circuits may be similar to those shown onpages and 61 (and de scribed on'the adjacent pages) of AutomaticTelephony, by Smith and Campbell, first edition, published by McGrawHill Book Co., Inc. New York City.

In Onc Y, a will be noted that the a;

peater R2 is inserted between the trunk line from the ofiice selectorbanks and the incoming thousands selector S3 in office X. This repeaterhas functions similar to those of the repeater R1 in office X, and ithas the additional function of translating the control received from thefirst selector repeaters in office Y into the regular two-wire loopcontrol to operate the switches in office X. The circuits of therepeater R2 are shown in full in Fig. 6 and will be described herein.

It will be noted that there is a toll line shown incoming to the ofliceand terminating in the selector repeater SR1, the banks of which aremultipled with the banks of the first selector repeater SR2. This tollline is shown more fully in Fig. 5 and it originates in a remoteexchange at a toll board and connections thereover through the automaticswitches are set up with either of the offices X or' Y or with any ofthe other ofiices of the exchange.

Reference may now be had to Figs. 2 and 3 which show a certain amount ofthe details of the circuits of the switches which may be used in settingup a connection from substation A3, Fig. 1, to substation A44. Theseswitches are the lineswitch LS2, the selector repeater SR2, thethousands selector S5, the hundreds selector S6, and the connector C2.Since the circuits of these switches are old and well known, only somuch of the circuits as are of utility in understanding the cooperationof these switches with the remaining part of the system have been shown.

A description oi. the operations taking place during the setting up of aconnection from the line of substation A3, Fig. 2,-to the line ofsubstation A4, Fig. 3, will now be given.

When the receiver is removed at substation A3, the usual loop controlcircuit is closed over the two conductors of the calling line, and thelineswitch LS2 starts irom its home position and searches for an idletrunk: in the usual manner. 'VVhen an idle trunk line is encountered,for example, the trunk line comprising conductors 218-22O and extendingto the first selector repeater SR2, an operating circuit is closed forthe combined switching andcut-otf relay 201 over the test and releasetrunk conductor 219, through theupper winding 01 relay 211 of SR2 andthe ofi-normal contacts 213. Relays 211 and 201 operate in series andrelay 201 shuntsits high resistance upper wind ing so as to place aguarding potential on conductor 219 through its low resistance lowerwinding. The marginally adjusted meter M does not operate at this timein multiple with the lower winding of relay 201. As a result of theoperation of relay 201, the wipers 202 and 204 are connected up to thecalling line, whereupon line relays 207 and 208 in the selector repeaterSR2 operate. Relay 208 closes a circuit for release relay 209, whereuponrelay 209 operates and prepares the switch for operation.

lVhen the calling subscriber dials the first digit 6 in the numberof thesubstation A l,

line relay 203 falls back six times and brings about the operation ofthe vertical magnetfnot shown) of SR2 in the usual by the verticalmovement, are rotated over the bank contacts in the sixth level insearch of an idle trunkline. hen an idle trunk line is reached, acircuit is closed over test wiper 215 for the test and switching relay212 from ground at the upper armature of release relay 209 through thelower winding of the release relay of the switch (the switch forexample) to which the idle trunk extends. the rotary movement in theusual manner, shunts its high resistance upper winding, so as to makethe seized trunk busy, and connects up the wipers 214tand 216.

In the selector'S5, relay 231' operates and prepares the switch foroperation, closing a connection between the test and switching relay 231 and the test wiper 236.

When the calling subscriber dials the second digit 1 in the number, linerelay 208 falls back once momentarily and grounds the upper talkingconductor, thereby operating the impulse relay 232 of the selector S5.Relay 232 causes the operation of the vertical magnet (not shown) of theselector S5 in the usual manner. At the same time, re lay 208 in theswitch SR2 operates the slow acting relay 210, whereupon battery isconnected through the lower armatures of relays 209 and 210 to the lowertalking conductor. As a result, the changeover control relay 233 in theselector S5 operates and prevents the rotary movement of the selectorfrom starting until the vertical movement has been terminated. I

lV hen relay 210 falls back at the end of the digit and opens thecircuit of relay 223, the latter relay falls back and initiates therotary operation in the usual manner. When an idle trunk line isreached, for example the trunk line extending to the selector S6, Fig.3, relay 23% operates through test wiper 236 and over conductor 1205Relay 234i shunts its high resistance winding so as to place a busypotential on the seized trunk line and it disconnects the incomingconductors 217 and 219 from relays 232 and 233 and connects them to thewipers 235 and 237. it

Bela 212, in addition to stopping Hill may be pointed out at this timethat the function of the off-normal contacts 213 and 230 is to increasethe resistance of the associated circuit when the oil-normal movementoccurs so as to cut down the holding current.

lVhen the next digit 2 is dialled, relay 302 oi the selector S6, Fig. 3,is operated twice over conductor 419 by the line relay208 of SR2. In theusual manner, relay 203 brings about the vertical operation of S6, withthe result that the wipers 305-307 are raised opposite the second levelof bank contacts. Relay 303 is operated throughout the vertical movementby relay 210 of the switch SR2, and it falls back at the end of thevertical movement to initiate the usual trunk hunting operation.

lVhenan idle trunk is reached, for example the trunk extending toconnector C2, relay 30st operates and makes the seized trunk busy, inaddition to extending the incoming conductors 4:19 and 421 to thecorresponding conductors 321 and 323 of the connector C2 through wipers305. and 307.

In the connector C2, there is asequence switch having wipers 329 and330. In positions 1 and 2 of these wipers, the combined front bridge andback bridge relays 326 and 327 are connected to the incoming conductors321 and 323, respectively. The side switch arms are moved in the usualmanner from position 1 to position 2 at the end of the verticalmovement, and are moved from position 2 to position 3 at the end of therotary movement. If the called line is busy, the arms 329 and 330 remainin position 3 and the usual busy tone is transmitted back to the callingline. However if the line is idle, the busy tone is not placed on thecalling line and the side switch arms 329 and 330 advance into positionat when the called. subscriber answers.

then the calling subscriber dials the tens digit 3, relay 326 isoperated three times over conductor 321, resulting in the usual verticaloperation. Vipers 331333 are thereby raised opposite the third level ofbank contacts. Relay 327 is operated over conductor during the verticaloperation, and when it falls back at the end of the vertical movement itsecures the advance of the side switch arms from position 1 to position2 in the usual manner.

\Vhen the calling subscriber dials the units digit 1, impulse relay 326of the connector C2 again responds and brings about the rotary movementof the switch in the usual manner. The wipers 331-333 are advanced onestep into engagement with the bank con tacts in which the conductors33l336 of thecalled line terminate. Relay 327 is operated againthroughout the rotary movement and it falls back at the end thereof,bringing about the advance or" the side switch through the heavyconductors. Relays 326 and 327 now operate over the called line, and theside switch arms 329 and 330 are caused to advance into position 4.

Conversation may now take place, talking current for the called linebeing supplied through back brid e relays 326 and 327 of the connectorG2, and talking current for the calling ine being supplied through linerelays 207 and 208 of. the selector repeater S32, Fig. 2.

The advance of side switch arm 330 into position at is for the purposeof preparing a circuit for causing the meter M, individual to thecalling line, Fig. 2, to be operated upon the release of the connector.It will be noted that the lower incoming conductor 323 of the connectorC is grounded through relay 327 in positions 1 and 2 of the side switcharm 330, and that it is connected to battery in position 3 through thehigh resistance 337 and relay 325. In position 4: (talking position) thearm 130 is,for the first time connected to battery through therelatively low resistance of relay 325. It will be seen therefore that adistinctive condition placed on the lower incoming talking conductoronly in case the called subscriber has responded and caused the sideswitch to pass into its fourth position.

When the conversation has terminated, the two subscribers replace theirreceivers. The replacing or the receiver at the called substation merelybrings about the cleanergization of relays 326 and 327, but does notproduce any other circuit changes as regards the incoming talkingconductors.

ll hen the receiver is replaced at the cal.- ing substation, relays 207and 208 fall back. Relay 20S opens the circuit of relay 209 and closesthe circuit of relay 210. Relay 210 accordingly operate Relay 210 placesbattery on the lower talking conductor as before, but this is of noparticular utility at this time. Itelay 210 it will be noted closesmultiple holding circuits for relays 211 and 212 at its upper armatureand at its inner lower armature. A moment later, relay 209 falls backand disconnects battery from the lower talking conductor at its lowerarmature, at, the same time connecting the lower talking conductor toground through the meter operating relay 217. Relay 217 now operatesover the lower talking conductor in series with relay 325 of theconnector C relay 325 being connected up by the side switch arm 330 inits fourth position. Upon operating, the meter operating relay 217, Fig.2, connects ground to conductor 219, thereby shunting relay 211 andincreasing the current flow over conductor 219 and through relay 201 ofthe lineswitch to such an extent that the meter M, bridged around thelower winding of relay 201, operates to record the completed connection.

A moment alter relay 209 falls back, relay 210 falls bad because itscircuit is opened at inner lower armature of relay 209. At its upperarmature, relay 210 removes ground from the lower terminal of relay 212;it removes ground from the lower terminal 01 relay 211 at its innerarmature; and at its lower armature it disconnects the lower talkingconductor from relay 217. As a result relay 217 also falls back anddisconnects ground at another point from coiuluctor 219. As a result ofthe removal of ground from conductor 219, the lineswitch LS2 is freedand it returns to its home position in the usual manner responsive tothe deenergization of relay 201.

As a result of the removal of ground from the lower terminal of relay212, the trunk line Xtending to the selector S5 is rendered idle andrelay 212 falls back, disconnecting the wipers 214s and 216. Theselector repeater SR2 is now restored to its normal position by theaction of the release magnet (not shown). l fhen the normal position isreached, the off-normal contacts 213 reclose so as to pe nit the switchto be taken for use ago. 11.

Responsive to the freeing of the trunk line extending to the selectorS5, release relay 231. falls back and brings about the usual releasingoperation, at the same time disconnecting test wiper 286 so as todeenergize relay 23% and to tree the trunk line extending to theselector S6. in the selector S6, release relay 801 now falls back andbrings about the release of the switch and the disconnection of theswitching relay from the test wiper.

In the connector C2, release relay 32 1 falls back when the test wiperof the selector S6 is disconnected, and the releasing operation occursin the usual manner.

Mention may be made at this point of the resistances 205 and 206 in theselector repeater wlich are connected between ground and the respectiveterminals of the condenser associated with the right-hand repeating-coilwindings. These resistances are relatively high and their function is topermit a small current flow over the talking conductors of theestablished. connection during conversation, one reason advanced forthis being that a quieter circuit results. The battery connections tothe talking conductors at this time are in the connector C2 through therelay 325 and the high re sistance 328.

he establishment and release of a connection local to oiiice Y havingeen explained hereinbefore and the establishment and release of aconnection in the otlice X being as explained in the Smith and Campbellpublication hereinbeiiore referred to, the expla- 112 ion ofinter-connections between the two ol'lices may now he proceeded with.For this purpose it will be assumed first that the subscriber atsubstation A1, Fig. 1, in otlice X desires to converse with the subscriber at substation A l in cities Y The substation A4; it will benoted is shown in 1 and also in Fig. 3.

Referring first to Fig. 1, the lineswitch LS1 extends the calling lineto a selector such S1 when the receiver is removed at substation A1. lVhen the first digit 6 is dialled, the selector S1 operates to raise itswipers (not shown) opposite the sixth level and to rotate them over thebank contacts in search of: an idle trunk line. It will be assumed thatthe trunk line extending through the repeater R1 to the selector SR3 incities Y is the one selected. In this case, the repeater R1 responds toits seizure in the'manner pointed out in the above mentioned Smith andCampbell publication and closes a bridge across the associated outgoingtrunk conductors. The detailed circuits of the selector SR3 in oilice Yare shown in Fig. 1, to which drawing reference will now be had.

When the bridge is closed across the incoming conductors 4 .01 and 402by the distant repeater R1 in oiiice X, the line relay 40 1-, which isbridged across these conductors through contacts of the reversing relay403, operates and closes a circuit for release relay 405. Release relay105 operates andprepares the switch for operation. I

lVhen the calling subscriber dials the next digit 1 in the desirednumber the bridge across conductors 401 and 402 in the repeater R1 isopened once momentarily, whereupon relay 10 i falls back momentarily.When it does so, it closes a circuit through the inner lower armature ofrelease relay 105 for series relay 406. Relay L06 operates and opens apoint in the circuit of rotary magnet 413. A circuit for vertical magnet115 exists in parallel with relay 406 through an armature of the testand switching relay 4-10. Accordingly, vertical magnet 4:15 is momentarily operated to raise the wipers ilo- 118 op posite the first level ofbank contacts.

When the slow acting series relay 106 falls back after the verticalmovement has been eilected, it completes at its inner lower armature acircuit'lor rotary magnet 113 which has been prepared at the oil-normalcontacts 1 This circuit includes the lower armature of the auxiliaryrelease relay L00 and the its circuit is closed,magnet 413 operates andadvances the wipers 416-418 into engage ment with the first set of bankcontacts in the level opposite which they have been raised, Near the endof its stroke, magnet 413 closes a locking circuit for itself throughthe armature of stepping relay 408 and it closes a circuit for the lowerwinding of the said stepping relay. Relay 408 operates and opens thecircuit of the rotary magnet, whereupon the rotary magnet falls back andopens the circuit of the stepping relay. In

case the trunk line termining in the first set of bank contacts isidle,'the test and switching relay 410 now operates through both of itswindings .in series, stopping the rotary movement. If the first trunkline: is busy however the rotary magnet circuit is not opened and therotary magnet operates again advancing the wipers another step. Thisalternate operation of the rotary magnet and the stepping relaycontinues as described until an idle trunk lineis reached, which trunkline, it will be assumed, is the one comprising conductors419-421 andextending to the hundreds selector S6, Fig. 3. When said idle'trunk'isreached, relay 410 operates through test wiper 417 and over conductor420, both windings being .connected in series between the test wiper andground at the inner lower armature of the auxiliary release relay 409.Upon operating, relay 410 disconnects the vertical magnet 415 at itsmiddle lower armature; opens the rotary magnet circuit and shunts itshigh resistance upperwinding' at its inner lowerv armature; and at itsupper and lower arma tures connects up the line wipers 416 and 418.

In the seized selector S6, Fig. 3, relay 301 operates over release trunkconductor 420 and prepares the switch for operation in the usual manner.

WVhen the calling subscriber dialsthe hundredsdigit 2 in. the desirednumber, line relay 404 of the switch SR3,-Fig. 4, falls back twicemomentarily. Each time it falls back, it grounds the upper talkingconductor at its upper armature, with the result that impulse relay 302of the selector S6, Fig. 3, is operated twice over conductor 419. Inaddition, the line relay 404 of the switch SR3 closes a circuit forseries relay 406 each time it falls, back, with the result that relay406 operates and remains operated throughout the digit. At its lowerarmature, relay 406 connects battery through the lower talking conductorthrough wiper 418 so as to operate the change over relay 303 in theselector S6, Fig. 3.

At the end of the hundreds digit 2, line relay 404 comes to rest inan'energized condition and relay 406 shortly falls back and removesbattery from the lower talking conductor.

. -Responsive to the digit transmitted to it the selector S6, Fig.3,-operates in the-usual manner and extends the connection toa'connector, such as connector C2. 7

' WVhen the neXttwo digits 3fl-and 1 are diallechthey are repeated bythe selector repeater SR3, Fig. 4, in the above manner with theresult-"that the connector C2 is caused to bring its wipers 331-333 intoengagement with the bank contacts of the called line. Assuming that thecalled line is idle and that the subscriber at substation A4 responds,the side switch arms 329 and 330 are caused to move into their fourthposition;

It. may be pointed out that the supervisory relay407 is normallyconnected between ground and the lowerv line wiper 418 of the selectorrepeater SR3. This relaydoesnot operate while the side switch arm 330'of the connector C2 is in third position owing to the high resistance ofthe resistance element 337, this element being provided for a purposewith which we need not be-cons cerned in the present. case. 3 However,when the side switch arm 330 reaches position 4 when the calledsubscriber responds, supervisory relay 407 inthe selector repeater SR3operates in series with relay 325.013 theconnector G2 and closes acircuittor'the revers ing relay 403. The reversing relay 403' re.-

verses the connection between the conductors 401 and 402 and the linerelay 404 so .as to bring. about a reversal in the direction of currentflow in the said conductors 401 and 402. v This causes the usualreversal of current flow in thecalling line to be made at. the repeaterR1 in the calling ofiice,-Fig. 1.

This latter reversalinay be made use of to operate a meter it'sodesired, or to give supervision in those cases where thecallxis coming"from an operator in a private branch exchange, or the ike. I v f Theconversation may now take place, and, when it has been terminated, thetwo subscribers replace their receivers. .When the receiver is replacedat the called substation, the battery teed relays 326 and 327 merelyfall back, but the remaining circuits shown remain in the samecondition.

When the receiver is replaced at the calling substation A1, Fig. 1,'therepeaterRl permits the release of the selector S1 andthe lineswitch LS1and opens the bridge across the conductors 401 and 402 of the selectorrepeater SR3, Fig. 4. When the bridge across these conductors in therepeater is opened, line relay 404 of the selector repeater falls backand opens the circuit of release relay 405, at the same time operatingrelay 406 which opens a point inthe talking circuit at its'lowerarmature, therebypermitr ting relay 407 to fall back. This operation ismore or less incidental at this time,;but it results in thedeenergization of the reversing relay 403, without however any particu-1511 efiiect being produced. A moment later release relay 405 falls backand opens the circuit of relay 406, at the same time opening the circuitof the auxiliary release relay 409., Relay 409 falls back and opens theconnection between test wiper 117 and ground, resulting in the releaseof relay 110 and in the freeing of the trunk line extending to thehundreds selector S6, Fig. 3. As a further result of the deenergizationof relay' l05, the usual release magnet circuit is closed throughoft-normal contacts 312. Magnet 311 now operates and restores the switchto normal in the usual manner. The switches S6 and C2 release in theusual manner.

i The manner in which connections are completed from ofiice Y to ofiiceX will now be explained. For thispurpose it will be assumed that thesubscriber at substation A3, Figs. 1 and 2 desires to converse with thesubscriber at substation A2, Fig. 1. It will be assumed further that thelineswitch' LS2, Fig. 2, seizes the selector repeater SR2 when thereceiver is removed and that the selector repeater SR2 finds the trunkline comprising conductors 220222 and extending to the repeater R2, Fig.6, idle when it rotates over the bank contacts in the fifth levelresponsive to the dialling of the first digit 5. That 7 being the case,relay 212 of the switch SR2 operates over the test conductor 221 inseries with release relay 601 of the repeater R2 when the idle trunk isreached. Relay 212 short circuits its upper winding so as to make theseized trunk busy in the usual manner.

In the repeater R2, the slow-to-pull-up relay 601 operates shortly afterits circuit is closed and after a sutlicient time has been allowed forthe test relay of the selector repeater SR2 to operate. Upon operating,relay 601 removes the shunt from around its upper winding so as todecrease the holding current, and it prepares a circuit for relay 603and closes a circuit through the lower winding of the electro-polarizedrelay 60%. This lower winding is the high resistance polarizing windingand the current flow through it is not of a sufficient value to operatethe relay. As a further result of the operation of relay 601, a bridgeis closed across the outgoing trunk conductors eX- tending to theincoming selector S3, 1,-

in office X. This bridge includes, in addition to the lower armature ofrelay 601, the lower armature o'f'impulse relay 602, impedance coil 605,and the upper winding of-electro-polarized relay 604. Responsive to theestablishment of this bridge, the distant selector S3 is prepared foroperation in the usual manner, the upper outgoing trunk conductorextending to battery through the upper winding of the line relay of theselector and the lower outgoing conductor ex- 7 sistance is insertedtending to ground through the lower winding ofthe said line relayAlthough cur.- rent is now flowing through both windings of theelectropolarized relay, the relay is not operated owing to the fact thatthe current .is flowing in opposite directionsin the two windings. Whenthe calling subscriber dials the second digit 1 in the desired number,the upper talking conductor extending from the switch SR1 to therepeater R2 is grounded once momentarily by line relay 208., Fig. 2,with the result that relay 602 in the repeater operates oncemomentarily, 1 opening the bridge across the outgoing conductors at itslower armature. Change-over relay 606 is operated at the the same timeover conductor 222 by series relay 210, Fig. 2. Relay 606 disconnectsthe upper talking conductor from the associated talking condenser andconnects it instead to the lower talking conductor by a more directpath, excluding the impedance coil 605 and the upper winding of theelectro-polarizedrelay 604-, so as to reduce the impedance of the bridgeduring impulsing. After the digit has been trans mitted, relay 606 fallsback. The distant selector S3 in oilice X, Fig. 1, responds to the digit1 and selects an idle hundreds selector, for example the selector S4.

When the neXt digit 2 is dialled, the selec tor See, Fig. 1, responds tothe impulses re peated to it by the repeater R2, Fig. 6, and raises itswipers opposite the second level, selecting an idle connector, forexample the connector C1.

When the last two digits 3 and 0 are "dialled, the connector G1,responds to the impulses repeated to it from the repeater R2, Fig. 6,and completes the connection to the line of substation A2. Ringingcurrent is applied in the usual manner when the connection is completed.

When the called subscriber responds by removing his receiver, thecurrent flowin the conductors incoming to the connector is reversed inthe usual manner by the connector, whereupon the electro-polarized relay604-, Fig. 6, responds as the current flow in its two windings is in thesame direction. Upon operating, relay 604 closes a circuit forsupervisory relay 603, whereupon relay 603 locks itself independent ofrelay 604. At its upper cuits, as regards the incoming conductors, intoa condition to simulate the condition placed 011 the incoming conductorsof the connector, Fig. 3. Specifically, a high rein series with impulserelay 602 atthe upper armature of relay 603, and the upper terminal ofchange-over rela 606 is shifted from ground to battery at t ie innerupper armature of relay 603 so as to place the necessary batterypotential armatures, relay 603 places the cir on conductor 222 to permitthe meter M of the calling subscrlber to operate when the conneet10n 1sreleased.

The conversation may now take place over the established connection.When the conversation has terminated, the subscribers replace theirreceivers. Then the receiver is replaced at the called substation, thecurrent flow in the conductors outgoing from the-repeater R2, Fig. 6, isreversed back to normal, whereupon the electro-polarized relay 604restores. Relay 603 however remains operated because of. itsloclring'circuit.

When the receiver is replaced at the calling substation, the meter M ofthe calling line is operated in the hereinbefore described manner afterwhich'the selector SR2 frees the trunk line extending to the repeater R2and restores to normal, in addition to freeing the lineswitch LS2.

hen the trunk lineextending to the repeater R2 is freed, release relay601. falls back and opens the bridge across the outgoing trunkconductors at its lower armature, at the same time opening the holdingcircuit ofrelay (S03 and the polarizing cir cult of relay 604 at itsinner lower armature.

Responsive to the opening of the bridgeacross the outgoing conductors,the switches in oflice X release in the usual manner.

It will now be explained how connections are completed over the incomingtoll line Figs. 1 and 5 to the exchange containing the oflices shown inFig 1. It may be. pointed out here that the exchange containing the tollboard through which the connections set up over the incoming toll linesare completed is a manual exchange and that a 24r-volt battery is usedtherefore at the toll board instead of the iS-volt battery ordinarilyprovided in automatic exchanges. That being the case, it is desired toimpulse over the incoming toll lines with the 48-volt battery at theautomatic'exchange rather than with the 24-volt battery at the manualexchange, as the higher voltage gives better operation, especially inview of varying ground potentials that may be encountered between theground connections at the two exchanges. In view of the foregoing and inview of the fact that the so-called dry trunk supervision is desired,certain special circuit provisions are necessary in connection with theimpulsing and supervision over the toll line as will be pointed outhereinafter.

Assuming now that the toll operator at the cord circuit CC desires toset up a connection through the cord circuit CC and over the toll lineto the exchange including offices X and Y, to thc'subscriber atsubstation A l, the upper spring contacts of the jack J close a circuitfor the release relay 553 when the plug is inserted into the jack. Relay553 operates and closes a circuit for the slow acting relay 552. Relay552operates and prepares a circuit for releasing'the distant connectionafter it is setup, this circuit being prepared at its upper, armature,and it closes a locking circuit for itself through the armature of relay551. As a further result of the operation of relay 558, the impulseconductor terminating in the upper. armature of this relay is connectedtoground through contacts of the key K and the supervisory relay 55%.When this occurs, relay 554 oper ates over the aboveinipulse conductorand over the two sides of 'thctoll' line in parallel. Upon operating,relay 554 places ground on the sleeve of the aclr J, lighting thesupervisory lamp L in the cord circuit (1C.

In the distant excl iange, the line relay 505, whose lower terminal isconnect-ed to the 418- volt exchange battery, operates through theassociated impulseconductor and over the two sides of the toll lineinparallel, in series with the calling supervisory relay at the tollboard. Upon operating, relay 505 closes a circuit for the associatedrelease relay 506, whereupon relay 506 operates and prepares the switchfor operation, the auxiliaryree lease time.

The calling toll operator now throws her calling device hey K, therebydisconnecting the impulse conductor from supervisory relay 55 i andconnecting it to ground through the calling device Gil Belay 554 fallsback and the lamp L becomes extinguished. i

lVhen the operator turns the callingdevice CDin accordance with thefirst digit 6 in the number, six interruptions are produced in thecircuit of the line relay 505 in the oiiice- Y, whereupon relay 505falls back momen-' tarily six times.

507 operates. and remains operated through out the series of impulses.Vertical magnet 51.7 is operated in multiple with relay 507 each time animpulse is delivered to the d relay. Theresult is that the wipers 518520 are r ised step-by-step opposite the sixth level on bank contacts.

When relay 507 falls back at the end of the vertical movement, it closesat its inner lower armature 'acircuit for rotary magnet 515 that hasbeen prepared at oii normal contracts 510. When the circuit of therotary magnet is closed, therotary magnet operates and advances thewipers into engagement with the first set of bank contacts, at the sametime locking itself inclependent of the test relay contacts and closacircuit for the stepping relay 510. The stepping. action is similar tothat described in connection with the selector repeater SR3,

Fig. 4. It will suffice to say then that when an ldle trunk is reached,for example the trunk line including conductors 217-'-219,

relay 511 being operatedat the same Each time itfalls back,. relay 505closes a circuit for the'slow actmg series relay 507, with the resultthat relay the rotary movement stops due to the energization of the testand switching relay 512 over the test conductor 218. Relay 512, it willbe noted, at its middle lower armature disconnects vertical magnet 517at its inner lower armature opens the rotary magnet cir cuit and shuntsits upper winding so as to make the seized trunk busy; and at its upperand lower armatures connects up the wipers 518 and 520.

As a result of the seizure of the trunk line comprising conductors2l72l9, the selector S5, Fig. 2, is prepared for operation in the usualmanner.

l i heu the calling operator dials the next digit 1 in the number, linerelay 505 of the selector repeater SP2 falls back once momentarily,sending one impulse over the upper talking wiper to the impulse relay ofthe selector S5. At the same time, slow acting relay 507 places batteryon the lower talking conductor of the trunk line through the wiper 520so as to operate the change over-control relay in the selector lheresult is that the selector S5 operates in the hercinbefore describedmanner to extend the connection to a hundreds selector such as theselector S6, Fig. 3.

lVhen the next digit 2 is dialled, the selector S6 operates in the usualmanner to extend the connection to a connector, for example theconnector C2.

lVhen the last two digits are dialled, the connector C2 operates in theusual mannerto extend a connection to the line of sul station A l.Assuming that this line is idle, the connection is completed and theside switch passes into position 4 when the called subscriber responds.l Vhen this take place, the supervisory control relay 508 in theselector repeater SR3 operates in series with r y 325 in connector C2and closes a circ .i for relay 504. Belay 504 closes a local holdingcircuit for relay 505 through the upper armature of relay 503, at thesame time disconnecting relay 505 from the incoming impulse conductorand connecting the said conductor to ground through the so-calledforced-release relay 503. Since he impulse circuit is now grounded atboth ends, the circuit having been restored to ground through thesupervisory relay 55% upon the restoration of the calling device lrey Kupon the completion of the dialing operatiou, with the result that therelay 55a reoperates at this time, relay 556i falls back andextinguishes the supervisory lamp L so as to inform the operator thatthe called subscriber has responded. The conversation may now take placein case the operator has completed the connection to the othersubscriber through the other plug of the cord circuit CC.

When the conversation has been com pleted, the two subscribers replacetheir receivers. The replacement of the receiver at substation A4 doesnot result in the relighting of the lamp L as a disconnect signal owingto the fact that the side switch arms of the connector do not move uponthe replacement of the receiver at the called station. However, theoperator obtains disconnect supervision in the usual manner from thelocal subscriber when he replaces his receiver. The operator thereuponpulls down the connection.

When the plug P is removed from the jack J, the'circuit of relay 553 isopened. Relay 553 falls back and opens the circuit of the slow actingrelay 552, at the same time connecting the impulse conductor through theupper armature of relay 552 and through the winding of relay 551 to the24e-volt battery. When this occurs, current from the 24-volt batteryflows over the toll line and operates relay 503. Relay opens the circuitof line relay 505 at its upper armature and at its lo T61 air-mature itcloses a multiple holding circuit for the supervisory control relay 508so as to main- .tain relay 508 operated for the time being.

Relay 505 falls back when its circuit is opened and it opens the circuitof release relay 506 and reoperates relay 507 through the lower armatureof relay 506. Relay 50? operates and disconnects supervisory relay 508from the lower talking wiper 520, but

relay 508 remains operated through the lower armature of relay 503.

At this point it may be mentioned, that, although the final result wouldbe the same in either case, it is to be assumed that the releaseimpulseis terminated at the toll hoard prior to the release of the slow actingrelease relay 506. lhe termination of the releasing impulse is broughtabout as follows: Relay 551 operates in series with the forced-releaserelay 503 of the switch SR3 and opens the locking circuit o-l 'rcleaserelay 5 2. Release relay 552 falls back after a slight interval andopens another point in its locking circuit, at the same time opening theforced release circuit at its upper armature.

In the selector repeater SR2, relay 503 now falls back and recloses theline relay circuit at its upper armature, at the same time opening thecircuit of relay 508 at its lower armature. 'l'lelayi508 falls back andrelay 505 reoperates. "Relay 508 however opens the circuit of relay 50d,whereupon relay 50-fl falls back and reconnects line relay 505 to theuugrouneed impulse. conductor,

t the same time disconnecting relay 503. Belay 505 new falls back againand the release or the switch takes place when the circuit of releasemagnet 513 is closed through oil-normal contacts 514 upon thedeenergization of release relay 506. 7

Considering now the release of the selector tion disclosed therein willbe explained.

repeater SR2 in case the operator pulls down the connection after anunsuccessful attempt has been made to set up a connection to a desiredline, it may be pointed out that relay 50a is not operated in this casebecause the supervisory control relay 508 is not operated unless acalled subscriber has responded. Therefore, when the impulse conductorthe trunk circuit TC is switched over from ground through thesupervisory relay 554C to the 2-t-volt battery tln'ouglrrelay 550 uponthe deenergization of release relay 553, relay 550 operatesas before,but line relay 505 remains operated due to the difi'erence in potentialbetween the t8-volt battery at the automatic exchange and the 24;voltbattery at the toll board. Then, when the slow acting release relay 552'in the trunk circuit TC opens the forcedrelease circuit, relay 505 fallsback and the release takes place as before.

Considering now the case when relay 552 is adjusted so as to releaseslower than the release relay 506, this will not have any effectdifferent than that described herein before except when a release takesplace after a called subscriber has responded. In this-case it will beremembered that relay 508 and relay 504 are operated when the forcedreleased circuit is closed. Relays 551 and 503 operate in series witheach other as before, and relay 551 opens the circuit of the slow actingrelay 552. Relay 503 opens the circuit of line relay 505, and the latterrelay in turn opens the circuit o'f'the slow acting release relay506.\Vhen relay .506 falls back, the release of the switch takes place inthe usual manner, but relay 503 remains operated and maintains relay 508o'p erated, which in turn maintains relay 504C ope ated until the forcedrelease circuit is subsequently opened by relay 552. Vhen this circuitis opened upon the deenergization of relay 552, the said relays 603,508, and 60 i fall back, and the circuits remain in this position untilthe toll line is again taken for use at .the toll board.

Referring now to Fig. 8, the modifica- 1n explanation of the utility of.thismodified arrangement, it may be pointed out that it may sometimeshappen that a considerable number of first selector repeaters such asselector repeater SR2, Fig. 2, are on hand when the toll lines such asthe one shown in Fig. 5 are installed between the toll board and theautomatic exchange. .3115 such is the.

case, it may be more economical to use these switches and provide arepeater R3, Fig. 8, between each toll line and a selector repeater suchas the selector repeater SR2, instead of providing entirely new switchessuch as the selector repeater SR3, Fig; 5. In this case, the selectorrepeaters are left un-' changed, except that two extra conductorsare'brought out fromthe terminals of the condenser in series with theright hand repeating coil winding, Fig. 8. The regular taken for use bya lineswitch such as LS2.

Line relay 801 also closes a bridge across conductors 1-18 and 420including the right hand repeating coil windings between the toll lineand the repeater, and the current limiting resistance 806. It may bepointed out that the resistance 806 and the associated condenser areused to avoid a saturation'of the core of the repeating coil as mighttake place if the two windings were connected directly together.Responsive to the closure oi. the bridge across conductors 418 and 420,the line relays of the selector, repeater SR2 operates as explained inconnection with the selector repeater SR2, preparing the switch foroperation.

lVhen the calling operator manipulates her calling device, relay 801responds and opens the bridge across conductors 4:18 and 120, whereuponthe selector repeater SR2" responds just as though a local callingsubscriber we're using the said selector repeater.

The supervisory control relay 804 has been provided to give supervisionto the calling operator when the calling subscriber responds, this relaybeing operated in multiple with the resistance 206 when battery througha sufiicieutly low resistance is placed on the lower talking conductorbythe connector when the called subscriber answers.

This maybe seen upon're'ference to the con-,

nector C2, Fig. 3. The impedance 805 is added so as to maintain thetalking circuit in a balanced condition. lVhen relay 804 operates, itconnects line relay 801 in alocal holding circuit through contacts ofrelay 802, atthe same time disconnecting the said line relay 801 tlromthe impulseconductor and connecting the impulse conductor to the:t'oreed-release relay 802/ This gives the hereinbetore-describedsupervision to the calling toll operator.

When the toll operator pulls down the connection, the impulse conductoris connected to the 2 l-voltbatteryat the switchboard in the abovedescribed manner whereupon relay 802'operates and opens thelcir cuitvofline relay 801. Relay 802 also closesa local holding circuit forrelay 804.

Inc

at the manual switchboard, relay 802 falls back and opens the circuit ofrelay i at the same time reclosinp; the circuit of line relay S01. Relay804 falls back and opens the local holding circuit of the line relay, atthe same time transferring it back to the impulse conductor. Linc relay801 thereupon again falls back. The release of the selector repeaterSR2, Which was temporarily halted. upon the momentary reoperation otlinerelay 801, now takes place due to the continued deenergization ofrelay 801.

ll hat is claimed is:

1. In amulti-ofiicc automatic telephone system, an automatic oilice inwhich talking current in local connections is supplied to bothsubscribers lines from the last. switch o'lt' thetrain, an automaticoilice in which talking current in all connections supplied to thecalling line from the first switch of the train and in which talkingcurrent in local connections is supplied to the called line lrom thelast switch. oi the train, and suitable circuit connections "forenabling talking connections to be set up from lines oli' either oiliceto lilies of the other oiiice, said talking connectionsincludingswitching mechanism in the called oilice which is also used to-set upconnections local to lines of such oliice.

2. In a multi-ofiice automatic telephoi'ie-sy tom, an automatic otiicein which talking current in local connections is supplied to both.subscribers lines from the last switch of the train, an. automaticoffice in which Milking current in all connections is supplied to thecalling line from the first switch of the train and in which talkingcurrent in local connections is supplied to the called line from thelast switch of the train, and suitable circuit connections for enablingtalking connections to be set up from calling lines in the first ofliceto called lines in the second oiiice through the medium of switchingmechanism which isalso used in setting up connections local to the linesof such oiiicc.

3. In a multi-oiiicc automatic telcphoncsystom, an automatic ofiico inwhich talking current in local connections is supplied to both subs;ibe'rs lines from the last switch of the train an automatic oiiicc inwhich talking current in all connections s supplied to the calling linefrom the first switch of the trainand in which talking current in local'(OilllCPilODFl is supplied to the called line from the last switch oithe train, and suitable circuit connections for enabling talking);connect-ions to be set up between ca ling lines of the second ollice andcalled lines of the first oflice through the medium o'fswitchingmechanism which is also used in setting; up connections localto thelines of such oliice.

site end when the called subscriber responds so as to give supervisionover the trunk line, and means at the opposite end of the trunk line formomentarily connecting the associated end of the impulse circuit to adi'l terent potential source so as to bring about the release of theconnection.

5. In a telephone system, a trunk line extending from a given point to adistant point, means at the said given point for closing a controlcircuit over said trunk line and for subsequently interrupting saidcontrol circuit to said digit impulses, automatic switching mechanismcontrolled over said trunk line from the distant end thereof to set up atelephone connection, loching means at the distant end of said-trunkline for stopping the current flow thereover when the call is answeredand for maintaining the connection intact, and means t the said givenpoint for terminating the locked up condition of the connection and forbringing about its release by momentarily reestablishing a current flowover said control circuit.

6. In a telephone system, means including a repeater, a trunk line, anda train of auto-- matic switches for setting up a connection to a calledline, connections in the last switch of the train for supplying talkingcurrent to the called line, two talking conductors incoming to saidrepeater, repeating means in said repeater controlled over said incomingtalking conductors in series for repeating impulses to the switches ofsaid train to secure their operation, said impulses being repeated overone talking conductor of said trunk line and a return path independentof the other talking condctor there-of, a supervisory relay'in saidtrunk line counectedto the other talking conductor, means in the finalswitch of the train responsive. to the answering of the calledsubscriber for operating said supervisory relay over a 0i"- cuit pathincluding said other talking (.Hlll" ductor and excluding; said onetalkiiur-conductor, and circuit connections in said re peaterresponsiveto the operation oi said supervisory relay to place adistinctive supiwvisory condition on "said incoming talking conductors.r

7. In a telephone systen'i, means inchuling a trun l: line and a trainof automatic switches iiQl SGlflilfl up a connection to a called line...said automatic switches being operated responsive to impulsestransmit ,dover one conductor of said-trunkline and. a return Fill lit)

over one conductor of said trunk line and areturn circuit independent ofthe other talking conductor, a supervisory relay connected. to saidother talking conductor, means in said trunk line for controlling thechangeover operation of the switches in said train over the othertalking conductor 01 the trunk line without operating said supervisoryrelay, and circuit connections in the last switch of the train forbringing about the operation of said supervisory relay when the calledsubscriber responds.

9. In a telephone system wherein a train of automatic switches isoperated over one talking conductor independent of the other and thechange over operation of the switches is controlled over the othertalking conductor independent of the first, means for transmitting hacka supervisory signal over the established connection to set up ananswered supervision state at the originating end thereof when thecalled subscriber answers.

10. In a telephone system, a trunk line, two trains oi automaticswitches, one train oi? switches being of the type arranged to respondto impulses over one talking conductor independent of the other and torespond to a changeover control over the other talking conductorindependent of the first, the switches in the other train being of thetype arranged to respond to setting impulses over both talkingconductors in series, a repeating device associated with said trunk lineand arranged to control the switches in the first mentioned train, and asecond repeating device between said trunk line and the second mentionedtrain arranged to suitably translate the control so that the secondtrain of switches may be operated responsive to the said controlexercised over the trunk line.

1].. In a telephone system, an impulse repeater having two incomingtalking conductors and two outgoing talking conductors, means in saidrepeater responsive to impulses received over an incoming talkingconductor for repeating impulses over an outgoing talking conductor,means for transmitting asupervisory signal back to said repeater overboth outgoing talking conductors in series, and means in said repeaterresponsive to said supervisory signal for transmitting'a supervisorysignal back over only one incoming talking conductor. x

12. In a telephone system, a repeater hav ing two incoming and twooutgoing talking conductors, means in said repeater for repeatingimpulses received over only one incoming talking conductor into acircuit including both outgoing conductors in series,

and means in said repeater controlled over an outgoing talking conductorfor placing a distinct supervisory condition on one of said incomingtalking conductors and for maintaining said distinct condition on suchconductor independent of further control over such outgoing conductor.

13. In a telephone system, a repeater having two incoming and twooutgoing talking conductors, means in said repeater for repeatingimpulses received over only one in comingtalking conductor into acircuit including both outgoing conductors in series, and means in saidrepeater responsive to a current reversal effected outside ofsaidrepeater over said outgoing conductors for ing two talkingconductors and having two-- outgoing talking conductors, meansresponsive to a selzure of said repeater over the incoming conductorsfor closing a bridge across said outgoing conductors, means 1n saidrepeater responsive to impulses received over the first lncommg talkingconductor for sending impulses over the outgoing talking conductors byinterrupting the bridge thereacross, means in said repeater responsiveto a prolongedimpulse received over the second incoming talkingconductor for reducing the impedanceof the bridge across the outgoingconductors during impulsing, a polarized relay in said repeaterresponsive to a current reversal in the outgoing conductors, andcontracts controlled by said relay for placing a distinctive supervisorycondition on the second incoming talking conductor. 7

15. In a multi-otiice automatic telephone system, an automatic oiiice inwhich talking current in local connections is supplied to bothsubscribers lines from the last switch of the train, an automatic oliicein which talking current in all connections originating therein issupplied to the calling line from the first switch of the train and inwhich talking current in local connections is supplied to the callingline from the last switch of the train, and suitable circuit connectionsfor enabling talking connectionsvto be set up from lines of eitheroffice to lines of the other oflice, saidcircuit connections includingsupervisory means controlled from the called office to give supervisionin the calling oflice.

Ill)

switch of the train, and suitable circuit connections for enablingtalking COHDOCJLIODS to be set up from lines of either office to hncs ofthe other oliice, said circuit connect-inns including means forindicating in the callinn o'lfice When'the calling subscriber in thecalled office responds.

Tn Witness whereof, I hereunto subscribe my name this 5th day of March,A. D.. 1592? JOHN WICKS.

